Illnesses such as the flu and colds are caused by viruses that infect the nose, throat, and lungs. They’re usually spread from person to person when an infected person coughs or sneezes.

They also can spread when a person touches cold or flu viruses deposited from another person on a desktop, doorknob, desk, telephone receiver, or handrail. Some viruses and bacteria can live for two hours or more on hard surfaces. If the person then touches his or her eyes, mouth, or nose before washing his or her hands, the viruses or bacteria gain entry to the body and infection can occur.

“Frequent hand-washing and practicing other healthy habits can protect everyone from getting or spreading germs at home, work, or school,” says Lola Russell, a spokeswoman for the CDC.

Flu prevention

The most important preventive measure against the flu is to get a flu vaccination every fall. The flu vaccine is offered as a shot for people of all ages or as a nasal spray for health adults who are younger than 49 and who aren't pregnant. The best time to get a flu shot is from mid-October to mid-November. Flu season runs from October to May, and it takes about two weeks after the vaccination for your body to form antibodies to protect you.

These people should not be vaccinated without getting clearance from their health care provider, the CDC says:

Those with severe allergy to chicken eggs.

Those who have had a severe reaction to the flu vaccine in the past.

Those who developed Guillain-Barré syndrome within six weeks of a previous flu vaccination.

Those with a moderate to severe illness that includes a fever. These people should wait until they have recovered from their illness.

Extra tips

These additional recommendations from the CDC can help you avoid getting and spreading infections at work and everywhere you go:

Avoid close contact with people who have colds or the flu. When you’re sick, keep your distance from others to protect them from getting sick, too.

Stay home from work when you’re sick. You’ll help prevent others from getting your illness.

Cough or sneeze into a tissue and then throw it away. Cover your cough or sneeze with your hand if you don’t have a tissue. Then, wash your hands.

Wash your hands often throughout the day. When soap and warm water are available, wash your hands by rubbing them together to clean all surfaces.

Don't touch your nose, eyes, or mouth. Viruses and bacteria can enter your body easily through any of these.

When soap and water aren’t available, use alcohol-based disposable hand wipes or gel sanitizers. For optimum effectiveness, check that the product is at least 60 percent alcohol. If using a gel, rub it into your hands until they’re dry.